The present invention relates to display devices equipped with plasma display panels and, more specifically, to a display device preventing any unwanted radiation noise from leaking to the outside.
Generally, such display device comes together with a circuit board on which a circuit driving the plasma display panel (hereinafter, referred to simply as PDP (Plasma Display Panel)) is arranged. The problem here is, such circuit driving the PDP easily generates electromagnetic waves as does subject electric signals to digital processing therein. The electromagnetic waves are also generated by PDP itself. That is, the PDP and its driving circuit are the source of unwanted radiation noise (hereinafter, referred to as EMI (Electro-Magnetic Interference). This is the reason why research and development for a display device having shielding effects has been active to prevent the EMI from leaking to the outside.
Such display device is the one, for example, disclosed in Japanese Patent Laid-Open Publication No. 9-172267. FIG. 25(a) is a slanted view showing the structure of the main body of the display device disclosed in the publication. FIG. 25(b) is a view of a section taken along with a one-dot chain line A-Axe2x80x2 shown in (a) of the same drawing, and viewed from the direction of an arrow B. In FIGS. 25(a) and (b), frames 251 are each made of a conductor typified by aluminum, and house a PDP and its driving circuit in a space enclosed thereby. Among those frames 251, a part placed at the rear of the display device is provided with a back cover 252, which is made of plastic. Also among those frames 251, a part placed at the front of the display device is provided with a front cover 253, which is also made of plastic. Therefore, approximately the entire parts inside of the front cover 253 are covered by the conductors (frames 253), and the main body can show the shielding effects.
However, the shielding effects thus provided to the above main body only suppresses the EMI leaking to the outside of the main body, and the EMI radiated from the PDP just loops to the driving circuit side. As a result, signal processing carried out by the driving circuit becomes problematically unstable.
Therefore, an object of the present invention is to provide a display device which can make a driving circuit stably operate with more satisfactory shielding effects.
The above object is attained by the following aspects. Here, those aspects include such specific limited matters as below, and therewith, specific technical effects are achieved.
A first aspect is directed to a display device for displaying a video on a screen thereof, comprising:
a plasma display panel (hereinafter, referred to as PDP(Plasma Display Panel)) structuring the screen;
a circuit board on which a circuit for driving the PDP is arranged;
a chassis formed like a plate made of conductive materials, to one plane thereof, the PDP is attached, and on the other plane thereof, the circuit board is mounted; and
an exterior unit being conductive, and housing the PDP and the circuit board having attached to the chassis, wherein
the chassis shields the circuit board so as to prevent any unwanted radiation noise emitted by the PDP from looping into the circuit on the circuit board,
the exterior unit prevents, with shielding effects, the unwanted radiation noise emitted by the internally-housed PDP and the circuit on the circuit board from leaking to the outside, and the chassis and the exterior unit are electrically insulated from each other.
In the display device according to the first aspect, the chassis shields the circuit, and the exterior unit shows shielding effects. With such double shield structure, the present display device first prevents any unwanted radiation noise emitted by the PDP from looping into the circuit on the circuit board, and thus the driving circuit of the PDP can stably operate. Further, with the double shield structure, unwanted radiation noise from the PDP and the circuit is stopped leaking to the outside of the exterior unit.
A second aspect is directed to a display device for displaying a video on a screen thereof, comprising:
a plasma display panel (hereinafter, referred to as PDP(Plasma Display Panel)) structuring the screen;
a circuit board having a circuit for driving the PDP is arranged on a substrate;
a chassis formed like a plate made of conductive materials, to one plane thereof, the PDP is attached, and on the other plane thereof, the circuit board is mounted;
a cabinet being conductive, and covering a front side of the chassis;
a back cover being conductive, and covering a back side of the chassis; and
a bracket being insulative, and fixed to the chassis so as to support the cabinet and the back cover, wherein
the cabinet and the back cover
are, when covering the chassis to which the PDP and the circuit board are fixed, supported by the bracket, electrically continued, and electrically insulated from the chassis, and thereby show shielding effects, and
the chassis is electrically insulated from the circuit, and thereby, shields the circuit board and prevents unwanted radiation noise emitted by the PDP from looping into the circuit.
In the display device according to the second aspect, the cabinet and the back cover house therein the chassis to which the PDP and the circuit on the circuit board are fixed, and electrical continuity is thus established. Therefore, the cabinet and the back cover both show shielding effects. Also, the chassis shields the circuit. With such double shield structure, the present display device first prevents any unwanted radiation noise emitted by the PDP from looping into the circuit on the circuit board, and thus the driving circuit of the PDP can stably operate. Further, with the double shield structure, the unwanted radiation noise from the PDP and the circuit is stopped leaking to the outside of the cabinet and the back cover.
According to a third aspect, in the second aspect, the display device further comprises an adhesive sheet used to attach the PDP to the chassis, and
the adhesive sheet is insulative.
According to the third aspect, the PDP can be easily attached to the chassis, and further, the PDP and the chassis can be electrically insulated from each other.
According to a fourth aspect, in the second aspect, in the chassis, a first boss is integrally formed,
the substrate is insulative, and in a predetermined position of the substrate, a through hole is formed, and
the circuit board is fixed to the first boss by a screw after inserted into the through hole, and thereby, the circuit arranged on the substrate and the chassis are electrically insulated from each other.
According to the fourth aspect, the first boss is integrally formed in the chassis, and thus there is no more need to structure a component in advance to attach the circuit board to the chassis. Accordingly, the number of components of the display device is reduced, and the manufacturing process of the display device can be simplified.
According to a fifth aspect, in the second aspect, the bracket is each attached to four corners of the chassis, and
the front cover and the back cover are both supported by the four brackets attached to each of the corners.
According to the fifth aspect, even if the cabinet and back cover are provided with some impactive forces, thus provided impactive forces are not directly given to the chassis, and absorbed by four brackets supporting the cabinet and the back cover. Therefore, the main components of the display device such as the PDP and the circuit board can be protected from the impactive forces coming from the outside.
According to a sixth aspect, in the second aspect, the display device further comprises a base being conductive, and determining a position of the screen with respect to a placement plane by having the chassis attached thereto, wherein
the base is electrically insulated from the chassis, and electrical continuity is established with the back cover.
According to the sixth aspect, the base is electrically insulated from the chassis, and electrical continuity is established with the back cover. Therefore, the reception sensitivity for the radio (video signal) is improved in the display device.
According to a seventh aspect, in the second aspect, the display device further comprises:
a top positioning unit having integrally attached to the chassis, and having a cylindrical hole whose center axis is parallel to a vertical direction opened from a flat lower end plane thereof;
an insulation layer formed inside, entirely, and on a lower end plane of the hole;
a base being conductive, and supporting the chassis so as to determine a position of the screen with respect to a placement plane thereof; and
a bottom positioning unit shaped like a rod, wherein
the base includes a lug in which a through hole is formed, a center axis of the through hole is parallel to the vertical direction, and an upper end plane thereof is formed flat,
the bottom positioning unit is fixed to the base by going through the through hole of the base and the hole formed in the top positioning unit, and thereby, the upper end plane of the lug determines a position of the lower end plane of the top positioning unit, and
the insulation layer makes the top positioning unit and the base insulated from each other.
With such structure according to the seventh aspect, the base is electrically insulated from the chassis, and electrical continuity is established between the base and the back cover.
According to an eighth aspect, in the second aspect, the display device further comprises a spacer made of conductive materials in which a first through hole is formed, wherein
in the chassis, a second boss is integrally formed,
at a predetermined position of the back cover, a second through hole is formed, and
a screw inserted into the first through hole and the second through hole is fixed to the second boss, and thereby, the back cover is attached to the chassis while kept electrically insulated therefrom.
According to the eighth aspect, the second boss is integrally formed in the chassis, and thus there is no more need to structure a component in advance to attach the circuit board to the chassis. Accordingly, the number of components of the display device is reduced, and the manufacturing process of the display device can be simplified.
Further, with the structure of the eighth aspect, the back cover is attached to the chassis while kept electrically insulated therefrom.
According to a ninth aspect, in the fifth aspect, among the four, the bracket attached on the chassis abuts to the inside of the back cover, and supports the back cover.
According to the ninth aspect, the bracket supports the back cover attached to the chassis. Therefore, displacement of the back cover hardly occurs.
According to a tenth aspect, in the firth aspect, the two brackets fixed on the chassis are each provided with a rib, and the rest are each provided with a screw hole,
the cabinet is provided with a hook on the upper part thereof, and a through hole on the lower part thereof,
the hook is engaged with and stopped by the ribs, and by the screw inserted into the through hole being fixed to the screw hole, thereby the cabinet is supported by the four brackets.
With the structure of the tenth aspect, the cabinet is attached to the chassis while kept electrically insulated therefrom.
According to an eleventh aspect, in the second aspect, the cabinet and the back cover touch to each other when supported by the brackets.
According to the eleventh aspect, electrical continuity is established between the front cover and the back cover by simply making those touch to each other.
According to a twelfth aspect, in the second aspect, the display device further comprises a base for making the chassis having the PDP and the circuit board attached thereto self-standing, wherein
the cabinet and the back cover are each detachable to the brackets.
According to the twelfth aspect, the cabinet and the back cover are each detachable to the brackets. Therefore, in order to access the inside of the display device, there only needs to remove either the front cover or the back cover. That is, according to the twelfth aspect, the accessibility to the inside of the display device can be improved.
According to a thirteenth aspect, in the second aspect, the display device further comprises an elastic solid being conductive, wherein
the cabinet and the back cover sandwich the elastic solid when supported by the brackets.
According to the thirteenth aspect, the elastic solid lies between the cabinet and the back cover and thus is closely attached to both of those. Further, the elastic solid is conductive, and thus helps to well establish electrical continuity between the cabinet and the back cover. Therefore, the shielding effects achieved by the cabinet and the back cover can be improved to a greater degree.